In U.S. Pat. No. 4,273,907 and Japanese Kokai 54/50067 organopolysiloxane compounds are described which have at least one benzoin group represented by the general formula ##STR2## where R is H or alkyl, bonded to a silicon atom in the molecule. Exemplified are compounds where R is H or methyl. However, it is well known that Si--O--C bonds readily hydrolyze and, in U.S. Pat. No. 4,391,963, it is noted that these photoinitiators are very unstable to moisture.
Another approach to providing polymer bound silicone polyphotoinitiators has been to prepare photoinitiator moieties with ethylenic or acetylenic unsaturation and then to react the photoinitiator with an SiH containing condensable silane or SiH containing polyorganosiloxane in the presence of a hydrosilation catalyst to give Si--C bound photomoieities. Such approach is taken in U.S. Pat. Nos. 4,273,907, 4,477,326, and U.S. Pat. No. 4,467,082.